Subglottal air pressure (Psub) is defined as:

• A. A measure of air pressure beneath the vocal folds necessary to initiate and sustain phonation.
• B. The average rate of airflow through the glottis during phonation.
• C. The amplitude of vocal fold vibration.
• D. The maximum phonation time.

Answer: (A)

Subglottal air pressure is the driving force from the lungs that sits beneath the vocal folds and must reach a sufficient level to start and maintain phonation. This pressure provides the energy the folds need to open and then continue vibrating, overcoming the tissue resistance and the closing forces so the oscillation can be sustained. In other words, it’s the air pressure behind the folds that initiates voice and keeps it going. It’s not the rate of air flowing through the glottis (that would be glottal airflow), nor the size of the vocal fold movements (vibration amplitude), nor how long you can sustain phonation (maximum phonation time).